Cameras and other wavelength-sensing devices use image pixels, such as complementary metal-oxide semiconductors, to detect wavelengths within a given wavelength spectrum. A voltage response of an image pixel is a function of the detected wavelength. For example, an image pixel detecting no visible light generates a voltage waveform that is different than a voltage waveform generated by the image pixel when exposed to white light. An analog-to-digital converter (ADC) is configured to convert voltage waveforms output by one or more image pixels into a digital domain.
One architecture of an ADC is a single slope ADC. In a single slope ADC, a ramp generator is configured to generate a substantially linear ramp signal that is compared to a voltage waveform output from an image pixel. The time it takes for the linear ramp signal to exceed the voltage waveform output from the image pixel is measured via a digital counter. A number of clock cycles that are counted by the digital counter during the time is used to derive a digital output that is equivalent to the voltage waveform, thereby converting the voltage waveform to the digital domain. A disadvantage of the single slope ADC architecture is the relatively long length of time it takes to perform an analog-to-digital conversion due to the linear nature of the ramp signal, resulting in high power consumption.